which aspects of LR might be predictive or have different mechanisms (Schuckit, Smith 1996;Schuckit, Smith 2000;Trim et al., 2009). Despite these difficulties, linkage and association studies have found some evidence for genomic localization of risk -promoting alleles for the global low LR phenotype [see, e.g., (Hinckers et al. 2006;Joslyn et al. 2008;Schuckit et al. 1999;Schuckit et al. 2001;Schuckit et al. 2005b)], although each such linkage signal may of course reflect the influence of only some particular aspect of low LR.
